Remove useless Meta-Action

Some Python class and packages need to be renamed
for a better compliance with the shared terminology
which provides a better understanding of Watcher objects
and components by every contributor.

Partially implements: blueprint glossary-related-refactoring

Change-Id: Ie0e33562f5e990c264a50ab3f533cfa62eac1d19

watcher/decision_engine/planner/default.py

@@ -124,7 +124,7 @@ class DefaultPlanner(base.BasePlanner):
                                                description="{0}".format(
                                                    action))
             else:
-                raise exception.MetaActionNotFound()
+                raise exception.ActionNotFound()
             priority = priority_primitives[primitive['action_type']]
             to_schedule.append((priority, primitive))